Blast furnace gas cleaning plants generally use a moving cone arrangement to control blast furnace top gas pressure and enable gas cleaning. The moving cone arrangement comprises an inverted cone having an open bottomed shell with supporting framework which is used to control gas flow and locally increase gas velocity as it passes over the cone. This improves trapping of dust particles in water droplets formed by water sprays impinging on the cone.
The arduous operating environment in this part of the blast furnace means that the cone is susceptible to both chemical attack and erosion. The cone is manufactured from materials chosen to maximise cone life, but the cone shell eventually fails. It is difficult to diagnose failure of the cone shell before it reaches a stage which starts to adversely affect plant performance, as the way the cone controls gas flow and maintains pressure means that it automatically compensates for minor wear in the cone shell. The first sign of failure of the cone shell may be by a gas monitoring sensor downstream detecting that the gas is getting dirtier again, but periodic inspections requiring a plant shutdown and isolation remain the most common condition monitoring method.